In this image of a combined silver-trichrome stain, the arrow points to the abnormal material within the arteriole lumen. This material was positive for IgM and showed kappa light chain restriction by immunofluorescence, supporting the diagnosis of paraprotein. Interestingly, this kidney biopsy was taken from an 81-year-old man with acute renal failure who had been diagnosed with Waldenström macroglobulinemia (his bone marrow biopsy showed involvement by lymphoplasmacytic lymphoma and he had a circulating IgM-kappa paraprotein).

A key point to remember is that monoclonal IgM paraproteins are associated with a wide spectrum of kidney diseases, including AL-type amyloidosis, cryoglobulinemic glomerulonephritis, and membranous glomerulopathy (see references below).

References:

A key point to remember is that monoclonal IgM paraproteins are associated with a wide spectrum of kidney diseases, including AL-type amyloidosis, cryoglobulinemic glomerulonephritis, and membranous glomerulopathy.